Method of adding liquid feed to a



Jan. 31. 1956 R. c. WOERNER 2,733,194

METHOD OF ADDING LIQUID FEED TO A FLUIDIZED COKER Filed April 25, 1950ELUTRIATOR- SUPERHEATER PREHEATER L Rudolph C.Woerner INVENTOR.

ATTORNEYS Unied m. Farm) Refining Company, New York, N Y.", acorporation of Maine ApplicationApril; 25,- 1950, Serial No. 157,871 3 cims.- or. 202

invention relates to improvements in the coking of hydrocarbon oils by.contacting the coking stock at a coking temperarure with a body ofadsorbentcoke particles nia'intained in a fluidized state in a cokingreactor from which large coke particles, are selectively withdrawn asformed" by elutriation and from which vapors are recovered overhead. Theprocess is described and claimed in application Serial No. 121,575 ofKenneth M. Watson filed October 15; 1949, now' Patent 2,707,702. Theprocess-has important, advantages in providing continuous cokingwhile.eliminating the difiiculties and cost of solid coke. relmovaliandhandling associated with conventional coking operations. My inventionconcerns a particular system-for. obtainingimproved initial contact andmixing at the cokingstock with the absorbent coke particles. In aparticular aspect, it concerns an improvedsystem in which,thecokingstockis. first segregated" into vapor and residualicomponents,the vapor components are directly introduced into the body of cokeparticles in the reactor so. as to assist fluidization and, the residualcomponents are separately contactedwiththe. coke particles accordingtoith'e improvedmixing. method of my invention.

Successful operation og the Watson. process requires maintenance of goodfluidiz'ation of the body of coke particles in the r eactor--so thatcoke formed from the heavy constituents of the coking stock can beselectively and etliciently absorbed on the coke particles, thusavoiding coking of the walls and plugging of the reactor and so thatlarge coke particles can be selectively withdrawn as coke is formed inthe process to maintain the system in equilibrium. The body of cokeparticles is supported as a dense phase fluidized bed approximating 35to 45 pounds per cubic foot in density, over a perforated conical grid.Fluidizing medium, usually steam, is introduced below the grid. Anelutriator opens into the bottom of the grid and an elutriation medium,usually steam, is supplied at a velocity permitting large particles tosettle from the reactor while retaining finer particles within thefluidized body. The preheated stock is sprayed directly into thefluidized body of the coke particles. I have found that spraying theusual coking stock, e.g. a reduced crude oil or heavy residuum, into thelarge body of coke particles maintained in the reactor often results inlocalized effects such as insufficient vaporization and agglomerationwhich interfere with satisfactory fluidization and which can result inlosing the bed.

According to my invention, the coking stock is injected into a stream ofcoke particles which is rapidly circulated from the main body of cokeparticles in the reactor through a confined conduit. Thus a stream ofcoke particles may be withdrawn from the bottom of the reactor bed bymeans of a standpipe and may be returned to the reactor by means of ariser discharging at a point near the top of the bed or into the upperportion of the bed. The coking stock is injected into the bottom of theriser so as to provide additional time factor for completion of thecoking reaction. The rapid circulation of the coke particles past thepoint of feed entry pro- 2 motes rapid and uniform dispersion anddistribution of the stock over the coke particles. The ratio of coke tooil obviously may vary considerably but with particular advantageis ofthe order of about 10:1 to 30:1 by weight.

An additional problem in economically operating a fluidized cokingprocess is the manner of supplyingsuflicient heat to the materials inthe reactorto attain optimum reduction of; thec oking stock to cokebothin terms of rate of reduction and maximum production of distillate oiluseful as. a makin charge stock. Thus rateof; coke make and overheadyield depend to a large extent upon high temperature. The cokingtemperature varies over the approximate range of 800 to 1290 F. butcommercial operation is conducted with advantage in the approximaterange of.875 to 1050 F; The most con: venient and least costly method ofputting the heat into the reactor is by preheating the coking feedstock, after the usual heat exchange, in a conventional fired heater tothe desired temperature or slightly above. At the higher temperaturesof,the coking reaction, say 950 to ZGSO R, coking difficulties areencountered inthe heater. in a particularly advantageous operationaccording to my invention, the coking stock is preheated-to, as high atemperature as possible withoutcoking the heater tubes, e.g. about 950 ri l V a flash chamber. Thehydrocarbonpartial pressure may be lowered bysteam introduction to prompteqseparation; The overhead vaporsaresuperheated to the de gs ired ing temperaturegwi-th minimumflme factonina second fired heater. The superheated are introduced. to the cokingreactor so as to assist in fluidizing the'body of coke particlesmaintained therein. Thus the vapors are introduced below the grid orinto a lower portion or the reactor bed. The heavy residuum is injectedinto the stream of coke particles rapidly circulated through theconfined conduit from the bottom of the reactorbed to the top of thebed. r I

In this manner, i obtain segregation of the coking feed'stcck so as topermit superheating the light oil com:- ponents at alow residence timeminimizing heater g in rd ro pp d ional: a wvthe ma eri s a. cokingreactor. The superheated vapors assist in fluidization and thus afford asubstantial reduction in the requirements for fluidizing steam.Advantageous vapor phase coking of the light oil components also isaccomplished. Improved mixing in terms of faster and more uniformcontacting between the heavy oil components and the absorbent cokeparticles is obtained.

My invention will be further described with reference to theaccompanying drawing which represents conventionally and somewhatdiagrammatically a flow plan embodying my invention. The coking stock isintroduced to preheater 10 and through line 11. Preheater 10 representsa conventional fired heater of the horizontal or vertical tube or coiltypes. The preheated coking stock is flashed from line 12 into flashchamber 13. Steam is introduced to the flash chamber through line 14 andthe overhead vapors are removed through line 15. The light oilcomponents of the coking stock comprising the overhead stream aresuperheated to the desired coking temperature, e. g. about l,000 to 1100F. in superheater 16 and from line 17 are passed into coking reactor 18.The superheated vapors are introduced below grid 19 above which a largebody of coke particles is maintained in a fluidized state. Reactionvapors are removed overhead from coking reactor 18 through line 19a andlarge coke particles are selectively removed from.- the bottom of thebed by means of elutriator 20 into which steam is introduced byconnection 21 for elutriation. A stream of coke particles is circulatedfrom the bottom of the body of coke particles in the reactor through aconfined conduit system comprising standpipe 22 and riser 23 back to apoint F., and the preheated stockis flashed innear the top of the mainbody of coke particles. The heavy residuum separated in flash chamber 13is conducted by line 24 under control of flow rate and level controller25 to the bottom of riser 23 where it,is injected into the stream ofcirculating coke particles through connection 25a. Dispersion steam maybe injected with the oil by means of connection 26 in order to promotedispersion of the heavy residuum. Where preliminary segregation of thecoking stock to light and heavy oil components is not desired, thepreheated coking stock may be directly charged to riser 23 throughconnections 27 and 25a. Fluidizing steam is introduced below grid 19 ofthe reactor 18 through connection 28. The reaction vapors removedthrough line 19a are conducted to a fractionating system (not shown) andmay be passed through an internal or external cyclone system to removeentrained coke fines.

In a typical operation, the reactor may be charged with to 30 mesh cokeparticles to form a bed of about feet by 50 feet, and the reaction isconducted at about 1000 F. Fluidizing medium is supplied to obtain avelocity of 2 to 3 feet per second through the bed and elutriating steamis supplied at about a linear velocity of 35 feet per second. A reducedcrude is charged to the system at the rate of about 100,000 pounds perhour and is preheated to about 950 F. before flashing into the flashchamber in the presence of steam charged at the rate of about 10,000pounds per hour. Overhead at the rate of about 80,000 pounds per hour issuperheated to upwards of 1000" F. before charging to the reactor. Heavyresiduum at the rate of 20,000 pounds per hour is charged withdispersion steam into the conduit through which coke is circulated at arate producing a coke to oil ratio of between about 10:1 and 30:1.

I claim:

1. In the coking of hydrocarbon oils by contacting the coking stock at acoking temperature with a body of 4 the circulating stream and chargingthe admixed stream to the upper portion of the reactor.

2. The improvement of claim 1 in which the ratio of coke to coking stockin the circulating stream is about 10:1 to 30:1 by weight.

3. In the coking of hydrocarbon oils by contacting the coking stock at acoking temperature with a body of coke particles maintained in a densefluidized bed in a coking reactor from which net coke make iscontinuously withdrawn selectively as large particles by elutriation andvapors are recovered overhead, the improvement which comprisespreheating the coking stock to about 950 F.,

, flashing the stock in a flash chamber, superheating the coke particlesmaintained in a dense fluidized bed in a coking reactor from which netcoke make is continuously withdrawn selectively as large particles byelutriation and vapors are recovered overhead, the improvement whichcomprises separately withdrawing a stream of coke par ticles from thelower portion of the reactor, rapidly circulatingsaid withdrawn streamof coke particles through a confined conduit, injecting heavy oil cokingstock into overhead vapors to a high coking temperature at low residencetime to minimize heater coking, introducing the superheated vapors tothe coking reactor so as to assist in fluidizing the body of cokeparticles maintained therein, separately withdrawing a stream of cokeparticles from the lower portion of the reactor, rapidly circulatingsaid withdrawn stream of coke particles through a confined conduit,injecting the residuum from the flash chamber into the circulatingstream and charging the admixed stream to the upper portion of thereactor.

References Cited in the file of this patent UNITED STATES PATENTS2,340,974 Myers Feb. 8, 1944 2,356,717 Williams Aug. 22, 1944 2,378,531Becker June 19, 1945 2,379,711 Hemminger July 3, 1945 2,394,651 AltherFeb. 12, 1946 2,426,848 Tuttle Sept. 2, 1947 2,427,112 Tyson Sept. 9,1947 2,445,328 Keith July 20, 1948 2,456,796 Schutte Dec. 21, 19482,511,088 Whaley, Jr. June 13, 1950 2,534,051 Nelson Dec. 12, 19502,543,884 Weikart Mar. 6, 1951 2,606,144 Leffer Aug. 5, 1952 OTHERREFERENCES Murphee et al.: Journal of the Institute of Petroleum,

vol. 33, N0. 286, pp. 608620.

Coke and Gas, September 1947, pp. 261-266.

3. IN THE COKING OF HYDROCARBON OILS BY CONTACTING THE COKING STOCK AT ACOKING TEMPERATURE WITH A BODY OF COKE PARTICLES MAINTAINED IN A DENSEFLUIDIZED BED IN A COKING REACTOR FROM WHICH NET COKE MAKE ISCONTINUOUSLY WITHDRAWN SELECTIVELY AS LARGE PARTICLES BY ELURIATION ANDVAPORS ARE RECOVERED OVERHEAD, THE IMPROVEMENT WHICH COMPRISESPREHEATING THE COKING STOCK TO ABOUT 950* F., FLASHING THE STOCK IN AFLASH CHAMBER, SUPERHEATING THE OVERHEAD VAPORS TO A HIGH COKINGTEMPERATURE AT LOW RESIDENCE TIME TO MINIMIZE HEATER COKING, INTRODUCINGTHE SUPERHEATED VAPORS TO THE COKING REACTOR SO AS TO ASSIST INFLUIDIZING THE BODY OF COKE PARTICLES MAINTAINED THEREIN, SEPARATELYWITHDRAWING A STREAM OF COKE PARTICLES FROM THE LOWER PORTION OF THEREACTOR, RAPIDLY CIRCULATING SAID WITHDRAWN STREAM OF COKE PARTICLESTHROUGH A CONFINED CONDUIT, INJECTING THE RESIDUUM FROM THE FLASHCHAMBER INTO THE CIRCULATING STREAM AND CHARGING THE ADMIXTURES STREAMTO THE UPPER PORTION OF THE REACTOR.